Power transmission



I 1,644,337 F. HYMANS v Oct. 4,

I'POWERTRANSMLSSION.

' Filed Oct. 14, 1922 v ATTORNEY Patented Get, 4, 1927 panes mm FREDERICK HYIVIANS OE PHILADELPHIA, PENNSYLVANIA.

POWER TRANSMISSION,

Application filed October 14, 1922. Serial No. 594,450.

My invention broadly relates to means, in association with transmission of 'power from a prime mover to a driven object, whereby objectionable periodic torsional vibrations are eliminated in the transmission system.

More specifically, my invention has special application to driving means between a slow running explosive engine of large power and a fast driven or high speed machine, such as a dynamo electric generator, wherein the speed of the driven machine is greatly increased over that of the engine. Engines of the Diesel'typeand large power are necessarily run at slow speeds and if'directly connected to an electric generator, the latter must be of large diameter and size and hence objectionable to such an' extent as to be commercially prohibitive. It, therefore, has been necessary to employ speed increasing gearing-between the, engine and generator so that the latter may be driven at the high speed necessary to insure predetermined output of energy. Such geared transmission has heretofore been objectionable for the following reasons: Primarily, the gearing to be successful, must be free from variations due to torsional fluctuations caused by variations in rotational velocity of the engine. As is well known, a Diesel engine is subject to very large periodic variations of torque and by reason of which, torsional vibrations become manifest at the gears, -a defect which is not removable even where very large fiywheels are employed in close couple with the engine and gears.

The object of my invention, therefore, is to provide means which will substantially eliminate objectionable torsional vibrations at the gears, thereby removing the objections heretofore existing to'the use ofa geared drive between the Diesel. orYequivalent engine and electric generator or other driven machine. p Y o i With the above and other objects in view, 45 the, nature of which will be more fully understood from. the description hereinafter,

the invention consists in the novel construction of power transmission, as hereinafter more fully described and defined in the claims.

Referring to the'idrawing: Fig. 1 is an elevation of a geared transmission between a Diesel engine and generator and embodying my improvements; Fig. 2 is a plan view of the same; and Fig. 3 is asimilar plan counteracted.

view showing a modification of myyinvention adapted to cases where the engine is to have capacity to be driven at a plurality of speeds.

In the several .figures of the. drawing, 1 is theDiesel engine, 4c is the electric generator or driving machine, 2 andB are the speed increasing gearing between the Diesel engine shaftand shaft of the generator, and 8 is the bearing-of the engine shaft nexttorthe gears 2. To these elements I provide additional means, to .bedescribed', whereby. all objectionable periodic torsional fluctuations inthe speed of the gears 2 is annulled or Assuming for example, that the engine has three cylinders, ,a study of the'crank effort diagram will show that said efl'ort sub} stantially consists of a constant torqueon which a third harmonic vibration is superposed. -The frequency of. the; periodic torque, due to the presence of thisthirdharmonic, is proportional to the. revolutions constant within the limits of a few percent by a suitable governor. Should there exist 'within the'engine onlyla single periodic torque of a definite frequency, which tends to cause fluctuations in the velocity of the gears 2, these fluctuations may be counteracted and substantially eliminated by novel means, comprising a shaft extension 5 in axial alinementwith the engine shaft, having secured thereona fly-wheel 6 at a distance from the gears, and said shaft supported by a suitable bearing 7. Theshaft 5 isin effect a torsional spring whose elasticity can be predetermined and established by the proper selection of. its quality, diameter and length. It will be understood that the flywheel being an inert mass, the .shaftand'flywheel together comprise anelastic system with capacity to respond totorsional vibrations of a definite frequency, and by the proper design they may be giventhe same frequency as that of theimpressed. periodic torque arising from the 'presenceof the third harmonic vibration due to'thevariations in rotational velocity of the engine.

If the system, last described, is attached to-the gears2 in the manner shown in Figs.

experimentally that-the fly whe el 6 will itselfvibrate in such a phase and with such amplitude as'to vwholly opposeand destroy the effect of the periodic torque on the gears 2, said gears then rotating ata perfectly uniformspeed, notwithstandingthe presence of a periodic torque in the'engine, This being accomplished, thegears 2 may be meshed with pinions 3' to uniformly drive a generator or: other'machine 4 at any predetermined speed without objectionable vibration. 7 It is sometimes desirable, in marine/installations, for example, to run'the engine at two definite speeds,v In that case,- the fre i quency of the periodic torque at one speed '1 fwill be' of=one degree or extent and at the other speed another or different degree or V extent." To counteract torsional fluctuations in the speed of gears'Q; it will be necessary to attach thereto an elastic'fsystem of the character" set out, but havingtwo'periods of free vibration withfrequenciesthe same as the frequencies of the; impressed periodic torque due to the twoflspeeds of-the engine.

This is I obtained by making the counteract 7 ing system one of two degrees of freedom;

. and'anjexample'of such a system is shown in' Fig. 3, which employs two elastic shafts 5 1and'10, respectively,- provided with flywheels 6jand 9. QWhere compensation is re quiredgfor" more than two variations in speed. the system may be extended to pro vide three cormo're degrees of, freedom, as

" Isa inay be necessary. f The arrangement, 3

' v 'ust described, is I also useful when the torque delivered by'the cylinders contains a plurality of harmonics of different frequencies. Strictly speaking, thisisalways the case although by proper design, it can be obtained that only" one of them is of sufficient magnitude and direction to become i manifest in 'vibrations .Nevertheless, in some cases, it occurs that next to the harmonic just mentioned there are others offdilferent frequencies whose magnitudes are sufiicient to make it desirable to nullify their tendency; to produce, such vibrations. In those cases, it isalso necessary to make the compensating system of as r many degrees of freedom withlas'many frefao;

quencies'as there are vibrations, due to har v monies,tocOunteract.

. Ivisedzanovel and useful construction which 3 It will" ow be apparent that I have de- 1 asjthesarne aresusceptible of modification in various particulars Without departing from the spirit or scope of the invention.

Having now described my invention, what I'claim as new and desire to secure by Letters Patent, is: a

1'. The herein descrlbed power transmis- S1011 drive, comprising a prune mover and its shaft, a machine to be driven, and transmission gearing between the shaft of the prime mover and the driven machine, combined with rotating means for counter-acting periodic vibrations of torque at the gearing, said means coupled to and in synchronous relation to the primeimoverand gearing, wherein the prime mover is arranged for running under a plurality of predetern'iined speeds and producesa 'cor responding periodic variation *of torque which is transmitted to the gearing, andwherein further the meansfor counteract ingit has a" corresponding plurality of periods of free VlbXEltlOIl, with frequencies corresponding to; the frequencies of impressed periodic torque due to the prime mover under its changes in'sped, whereby the periodic torsional vibrations of the gearing under the changes in speed are automatically counteracted.

2. The lnvention according to claim 1,

wherein the means for counteracting the J periodic torsional vibrations" in the gearing comprises a torsional spring shaft structure arranged to rotate synchronously with the shaft of the prime mover and the gearing driven thereby, and a plurality of fly-wheels secured to the shaft structure at spaced distances along its length.

SJThe herein descrlbed power transmis' sion drive, comprising a prime mover and its shaft, a machine to be driven, and transmission gearing between the shaft of the prime mover and the driven machine, which prime moverin operation produces variations of torque of. a plurality of frequencies corresponding vibrations, combined with rotating means for counteracting the plurality of ,periodicyvibrations due it the x prime mover, said means rotating in synchronlsm with the prime mover and arranged to counteractthe tendency jto"periodic vibrat ons in the transmission gearingand havlng a plurality of periods of free g torsional vibration. with frequencies substani which are. transmitted to the transmission gear ng and tending to produce. therein tially the saine'asthe frequencies of the im pressed torque of the prime mover.

unto set my. hand.

FREDERICK HYMANS,

In testimony of which invention, I here- 

